Human beings are created both in the image of God and to be the image of God in the life of the world.
Regarding the "in," human beings are created in God's image not as isolated individuals or as a generalized humanity, but as social, relational beings. They are thereby correspondent to the sociality of God witnessed to in the "let us" of Genesis 1:26; they are the product of an inner-divine communication. The "in" entails the entire person (including the body); as such, human beings are given such gifts that they have a communicating relationship with one another and with God.
Regarding the "to be," the God in whose image human beings are created is depicted in Genesis 1-2 primarily as one who creates and as one who shares power with the creatures in the task of creating (1:11, 20, 24, 26; 2:19-20). So human beings are to be thought of primarily in terms of creativity and imagination and not, say, domination and violence. This understanding informs the tasks to which human beings are called in 1:28: be fruitful, multiply, fill the earth, have dominion, and subdue the earth. God hereby gives power to the human beings to continue the human race and to bring order out of continuing disorder ("subdue").
Creation in Genesis 1-2 is not presented as a "finished product," all wrapped up with a big red bow and handed over to the creatures to keep exactly as it was originally created. God creates a dynamic world in which the future is open to a number of possibilities and in which creaturely activity is crucial to proper creational developments. For the creation to remain just exactly as God created it in the beginning would have been a failure of the divine design.
26 Then God said, Let us make humankind* in our image, according to our likeness; and let them have dominion over the fish of the sea, and over the birds of the air, and over the cattle, and over all the wild animals of the earth,* and over every creeping thing that creeps upon the earth.
27 So God created humankind* in his image,
in the image of God he created them;*
male and female he created them.
28God blessed them, and God said to them, Be fruitful and multiply, and fill the earth and subdue it; and have dominion over the fish of the sea and over the birds of the air and over every living thing that moves upon the earth.
New Revised Standard Version Bible: Anglicized Edition, copyright © 1989, 1995 National Council of the Churches of Christ in the United States of America. Used by permission. All rights reserved worldwide. http://nrsvbibles.org